The present invention relates to a device for removing bone tissue. More particularly, the invention relates to a device for removing bone tissue in which the cutting tool opens directly into a collection container that is under vacuum pressure. The container includes a filtering unit to collect the removed bone tissue that can be used, for example, as bone grafting material.
Implantation of endogenous bone material remains the most efficient method of management in cases of pseudarthrosis, for optimizing the success rate in arthrodesis and when a bone fracture fails to heal. The use of endogenous bone material is more reliable and more effective than the use of synthetic hydroxylapatite materials or exogenous bone grafts, but it necessitates an additional procedure on the patient""s body. This can be minimized by limited depth of penetration and by using a cylindrical needle, such as that used to remove bone material for diagnostic purposes. However, this technique is complicated and hazardous because precise control cannot be guaranteed. Therefore, in most cases, the cancellous bone is cut out through a larger skin incision and a large opening at the pelvic brim. Special bone graft collecting instruments permit a secure and reliable method of obtaining endogenous bone grafts through a small incision in the skin, which minimizes unpleasantness and injury to the patient. These devices remove the bone material reliably and can be used with a drill, so that a larger amount of bone can be removed and the possibility of control is better, and furthermore inadvertent puncturing of the cortical portion is minimized. This reliable and effective technique makes it possible to remove endogenous bone grafts for fusions, pseudarthrosis and bone fractures with minimal injury to the donor. Bone grafts are generally removed from the pelvic bone of a patient""s body. Usable bone material can also be obtained from the proximal ulna or distal radius.
A method and a device for harvesting tissue is disclosed in U.S. Pat. No. 5,403,317 to Bonutti. This known system comprises a device for percutaneous removal of tissue and consists of a flexible drill shaft and means for driving the shaft. A cutting tip is mounted on the distal end of the shaft for cutting tissue fragments out of the tissue. During the cutting operation, the tissue fragments are pulled through the shaft by a vacuum and collected at a location outside the body. One disadvantage of this known device is that the bone grafts are conveyed through a tube under a reduced pressure, moving them away from the cutting device to a filter or a separation device. The resulting long conveyance pathways for the bone grafts require a strong vacuum on the end of the conveyor line at a distance from the cutting head and offer the possibility of unwanted deposits of bone grafts inside the conveyor line, especially at bends in the line.
International Publication No. WO 97/39685 of Yuan teaches an apparatus for harvesting bone material that has a rigid, transparent shaft in the form of a hollow cylinder wherein the bone chips are collected, the quantity of collected chips being easily visible due to the transparent shaft, a cutting head arranged on the one end portion and means for receiving a turning moment arranged on the other end portion of the shaft. The apparatus is simply screwed into the bone, the cutting head having the function of cutting and removing chips of bone. The bone chips are received and collected in the cavity of the shaft. The collected bone fragments are then, as needed, removed from the shaft by means of a piston which is inserted into the cavity of the shaft from the side opposite the cutting head. As to the source of rotational drive power, the apparatus may be driven by hand or by motor.
Another apparatus of this type for harvesting bone material is known from U.S. Pat. No. 5,556,399 to Huedner. This known apparatus also includes a drilling head with an adjoining, rigid shaft in the form of a hollow cylinder in which the bone chips are collected and from which they are subsequently removed by means of a manually actuated piston which is to be introduced into the cavity from the side of the drilling head.
U.S. Pat. No. 4,646,738 to Trott discloses a device that has an exterior tube-like part and interior tube-like part, whereby at one end of the interior tube-like part a cutting tool is attached. The interior tube-like part is rotatably arranged within the exterior tube-like part, while the exterior tube-like part is manufactured of a deformable material and is selectively bendable. International Publication No. WO 96/39956 of Aust discloses a device that has a thin-walled hollow cylindrical shank which is externally enclosed through a spiral spring.
In general, these prior art devices suffer from the disadvantage that due to the torsional rigidity of the shaft, there is a risk of cutting or penetrating the harder cortical bone during the process of reaming the spongiosa lying between the cortical portion of the bone. Thus, a need exists for an improved device for removing bone tissue.
The present invention relates to a device for harvesting bone tissue with a cutting tool. The cutting tool can include a rotatable shaft with proximal and distal ends with an axial bore extending therethrough. The cutting tool also has a cutting head rotatably coupled with the shaft and having a through-hole operably associated with the axial bore such that bone removed by the cutting head passes from the through-hole to the bore. If the cutting head is detachable from the shaft, the connection between the cutting head and the shaft can be a screw connection such that it permits a smaller tool set for removal for assembly or disassembly. Other possible types of connections between the cutting head and the shaft include the use of radial pin screws or radial pin connections. The cutting head may also be configured such that it is integral or fixedly connected to the shaft.
The device also includes a drive element for rotating the shaft about the longitudinal axis and a handle for manually operating the device. The device further includes a container, having a central axis, detachably mounted to the drive element and operably associated with the cutting tool such that the central axis of the container is co-linear with the longitudinal axis of the cutting tool. The container is under vacuum such that the vacuum pressure suctions and removes bone from the through-hole to the container through the axial bore. The device is configured so as to permit simultaneous removal and suction of the bone tissue.
The handle is configured such that the drive element, cutting tool and container are freely movable by the handle.
The device can be configured such that the proximal end of the cutting tool opens into the container. The container remains fixed with respect to the longitudinal axis, and there is an airtight connection between the shaft and the container such that the proximal end of the shaft opens into the container and is isolated from the environment.
The container also includes a nozzle for connection of a vacuum line to create the vacuum pressure within the container. Additionally, the container comprises a separation element for separating the bone tissue from the air stream. The separation element can be a screen, filter, baffle, cyclone, or similar devices.
In one embodiment, the container comprises a gasket sealed ball bearing and housing for mounting the container to the shaft of the cutting tool. The gasket can be an O-ring gasket.
The shaft of the cutting tool can include a flexible portion to avoid damage to cortical bone. One embodiment of the flexible shaft is a metal strip wound in a spiral. The shaft can also include a tube composed of either rubber or plastic inserted into the bore of the shaft. Additionally, the wall of the shaft can be constructed like a bellows.
The cutting tool of the device can include a cutting head with a cylinder having proximal and distal ends and a hollow space therethrough. The distal end of the cutting head includes a drill tip with at least one cutting edge and at least one through-hole extending radially from the central longitudinal axis for the purpose of conveying removed bone tissue to the bore of the shaft. The drill tip can be shaped like a sector of a universal ball joint or a calotte sector.